1. Field Of The Invention
The present invention relates generally to the construction of knives and other sharpened implements, and more particularly to the construction of an integral cover to protect such an implement from damage and from damaging its surroundings.
2. Description Of The Prior Art
Knives and other cutting implements are necessarily sharpened in order to be useful. While being essential for their utility, the sharpened edge of a knife can present a danger to people and property when it is being stored or transported. This is particularly true of small utility knives which are frequently carried in pockets and purses where they expose the carrier to severe injury. Moreover, the knife blade itself can be dulled or damaged by storage in an unprotected manner under such conditions.
Recognizing these problems, a number of techniques have been developed for protecting knife blades when not in use. Perhaps the most simple method is the use of a separate blade sheath for covering the blade. The knife may be simply withdrawn from the sheath for use and returned to the sheath when not in use. The use of a sheath, although suitable for many applications, suffers from certain drawbacks. First, sheaths are easily misplaced and separated from the companion knife during use. A lost sheath provides no protection whatsoever. Second, the removal of the sheath requires two hands, while the user often only has one hand available to manipulate the knife.
To overcome these problems, other approaches have been developed for protecting knife blades. The most common is probably the pocketknife having a folding blade. Such knives include a handle having one or more articulated blades attached to the end(s). The blades may be unfolded and exposed for use, and folded back into the handle for storage. Such knives, although they enjoy wide popularity, are not suitable for all purposes. Many times it is desirable to use a fixed-blade knife where the blade is firmly attached to the handle. The articulated blades of pocketknives are subject to collapse during use and can cause severe injury to the user. Moreover, folding pocketknives are even more difficult to uncover and manipulate with one hand than fixed knives having separate sheaths.
Another type of knife which is a variation on the folding pocketknife is the spring-loaded pocketknife, or "switchblade" where the blade can be extended simply by pushing a button. The only advantage of such knives is that they can be opened using only one hand. Conversely, the knives suffer from a number of disadvantages. The knife blade opens very quickly, and accidental actuation can be very dangerous. Moreover, the extended knife blades are subject to accidental collapse which can injure the user in the manner just described for folding pocketknives. Thus, the spring-loaded pocket knife is not suitable for routine use.
Other safety knives and implements have been described in the patent literature. U.S. Pat. No. 4,091,537 to Stevenson, Jr. describes a safety utility knife having a spring-loaded blade guard. U.S. Pat. No. 2,644,230 to Anderson describes a carton cutter having a retractable blade guard. U.S. Pat. No. 2,512,237 to Mravik discloses a nail file having a retractable sheath which can be manually retracted into a handle and automatically extended from the handle.